3/9/18
here is the origin of the yield gap
note that the change is most of all yield per worker, but also
yield per acre
based on machinery, electrification, chemical inputs, plant and
animal breeding
machinery:
electrification:
- irrigation
- raising animals indoors requires heating,
cooling, and lighting
- refrigeration and easier household work
chemical inputs:
- fertilizer--nitrogen was most critical and
most expensive until after WWII, when TVA production of
explosives was turned to fertilizer. WWII to 1980 saw biggest
expansion
- insecticides based on arsenic were used from
the late 19th century, but there were substantial risks.
Modern insecticides were a product of WWII nerve gas research
- herbicides were developed after WWII and
removed the need to cultivate to keep down weeds
- antibiotics and hormones given to animals to
promote growth even in the absence of disease
plant and animal breeding
- hybrid corn introduced in 1925 but was slow to
catch on
- artificial insemination sped up the breeding
of animals that grew faster or produced more milk